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Ciucă Anghel DM, Nițescu GV, Tiron AT, Guțu CM, Baconi DL. Understanding the Mechanisms of Action and Effects of Drugs of Abuse. Molecules 2023; 28:4969. [PMID: 37446631 DOI: 10.3390/molecules28134969] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/18/2023] [Accepted: 06/22/2023] [Indexed: 07/15/2023] Open
Abstract
AIM Drug abuse and addiction are major public health concerns, with millions of people worldwide affected by the negative consequences of drug use. To better understand this complex issue, a review was conducted to examine the mechanisms of action and effects of drugs of abuse, including their acute and chronic effects, the symptoms of abstinence syndrome, as well as their cardiovascular impacts. METHODS The analyzed data were obtained after surveying an electronic database, namely PubMed, with no time limit, grey literature sources, and reference lists of relevant articles. RESULTS The review highlights the different categories of drugs of abuse, such as opioids, stimulants, depressants, hallucinogens, and cannabis, and discusses the specific ways that each drug affects the brain and body. Additionally, the review explores the short-term and long-term effects of drug abuse on the body and mind, including changes in brain structure and function, physical health problems, and mental health issues, such as depression and anxiety. In addition, the review explores the effects of drug abuse on cardiovascular health, focusing on electrocardiogram changes. Moreover, the analysis of relevant literature also highlighted possible genetic susceptibility in various addictions. Furthermore, the review delves into the withdrawal symptoms that occur when someone stops using drugs of abuse after a period of chronic use. CONCLUSION Overall, this review provides a comprehensive overview of the current state of knowledge on drug abuse and addiction. The findings of this review can inform the development of evidence-based prevention and intervention strategies to address this critical public health issue.
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Affiliation(s)
| | - Gabriela Viorela Nițescu
- Ward ATI-Toxicology, Paediatric Clinic 2, "Grigore Alexandrescu" Emergency Clinical Hospital for Children, 011732 Bucharest, Romania
| | - Andreea-Taisia Tiron
- Department of Medical Semiology, Sf. Ioan Emergency Clinical Hospital, Carol Davila University of Medicine and Pharmacy, 20021 Bucharest, Romania
| | - Claudia Maria Guțu
- Department of Toxicology, Carol Davila University of Medicine and Pharmacy, 20021 Bucharest, Romania
| | - Daniela Luiza Baconi
- Department of Toxicology, Carol Davila University of Medicine and Pharmacy, 20021 Bucharest, Romania
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Palma-Conesa ÁJ, Ventura M, Galindo L, Fonseca F, Grifell M, Quintana P, Fornís I, Gil C, Farré M, Torrens M. Something New about Something Old: A 10-Year Follow-Up on Classical and New Psychoactive Tryptamines and Results of Analysis. J Psychoactive Drugs 2017; 49:297-305. [DOI: 10.1080/02791072.2017.1320732] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Álvaro José Palma-Conesa
- Predoctoral Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Resident Psychiatry, Neuropsychiatry and Addiction Institute, Parc de Salut Mar, Barcelona, Spain
- Predoctoral Student, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
- Collaborator, Energy Control, Associació Benestar i Desenvolupament, Barcelona, Spain
| | - Mireia Ventura
- Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Manager, Drug Checking Service, Energy Control, Associació Benestar i Desenvolupament, Barcelona, Spain
| | - Liliana Galindo
- Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Consultant Psychiatry, Neuropsychiatry and Addiction Institute, Parc de Salut Mar, Barcelona, Spain
- Postdoctoral Student, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
| | - Francina Fonseca
- Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Senior Consultant, Neuropsychiatry and Addiction Institute, Parc de Salut Mar, Barcelona, Spain
- Assistant Professor, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
| | - Marc Grifell
- Predoctoral Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Resident Psychiatry, Neuropsychiatry and Addiction Institute, Parc de Salut Mar, Barcelona, Spain
- Predoctoral Student, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
| | - Pol Quintana
- Collaborator, Resident Family Medicine, Energy Control, Associació Benestar i Desenvolupament, Barcelona, Spain
| | - Iván Fornís
- Consultant, Drug Checking Service, Energy Control, Associació Benestar i Desenvolupament, Barcelona, Spain
| | - Cristina Gil
- Technician, Drug Checking Service, Energy Control, Associació Benestar i Desenvolupament, Barcelona, Spain
| | - Magí Farré
- Predoctoral Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Professor, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
- Head Senior Consultant, Clinical Pharmacology Unit, Hospital Universitari Germans Trías i Pujol, Servei de Farmacología Clínica, Badalona, Spain
| | - Marta Torrens
- Professor, Department de Psiquiatria i Medicina Legal and Farmacologia, Terapèutica i Toxicologia, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
- Head Researcher, Addiction Research Group, Neurosciences Research Program, IMIM-Hospital del Mar Medical Research Institute, Barcelona, Spain
- Head Senior Consultant, Addiction Program, Neuropsychiatry and Addiction Institute, Parc de Salut Mar, Barcelona, Spain
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Miliano C, Serpelloni G, Rimondo C, Mereu M, Marti M, De Luca MA. Neuropharmacology of New Psychoactive Substances (NPS): Focus on the Rewarding and Reinforcing Properties of Cannabimimetics and Amphetamine-Like Stimulants. Front Neurosci 2016; 10:153. [PMID: 27147945 PMCID: PMC4835722 DOI: 10.3389/fnins.2016.00153] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 03/21/2016] [Indexed: 01/19/2023] Open
Abstract
New psychoactive substances (NPS) are a heterogeneous and rapidly evolving class of molecules available on the global illicit drug market (e.g smart shops, internet, “dark net”) as a substitute for controlled substances. The use of NPS, mainly consumed along with other drugs of abuse and/or alcohol, has resulted in a significantly growing number of mortality and emergency admissions for overdoses, as reported by several poison centers from all over the world. The fact that the number of NPS have more than doubled over the last 10 years, is a critical challenge to governments, the scientific community, and civil society [EMCDDA (European Drug Report), 2014; UNODC, 2014b; Trends and developments]. The chemical structure (phenethylamines, piperazines, cathinones, tryptamines, synthetic cannabinoids) of NPS and their pharmacological and clinical effects (hallucinogenic, anesthetic, dissociative, depressant) help classify them into different categories. In the recent past, 50% of newly identified NPS have been classified as synthetic cannabinoids followed by new phenethylamines (17%) (UNODC, 2014b). Besides peripheral toxicological effects, many NPS seem to have addictive properties. Behavioral, neurochemical, and electrophysiological evidence can help in detecting them. This manuscript will review existing literature about the addictive and rewarding properties of the most popular NPS classes: cannabimimetics (JWH, HU, CP series) and amphetamine-like stimulants (amphetamine, methamphetamine, methcathinone, and MDMA analogs). Moreover, the review will include recent data from our lab which links JWH-018, a CB1 and CB2 agonist more potent than Δ9-THC, to other cannabinoids with known abuse potential, and to other classes of abused drugs that increase dopamine signaling in the Nucleus Accumbens (NAc) shell. Thus the neurochemical mechanisms that produce the rewarding properties of JWH-018, which most likely contributes to the greater incidence of dependence associated with “Spice” use, will be described (De Luca et al., 2015a). Considering the growing evidence of a widespread use of NPS, this review will be useful to understand the new trends in the field of drug reward and drug addiction by revealing the rewarding properties of NPS, and will be helpful to gather reliable data regarding the abuse potential of these compounds.
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Affiliation(s)
- Cristina Miliano
- Department of Biomedical Sciences, University of Cagliari Cagliari, Italy
| | - Giovanni Serpelloni
- Advisory and Steering Group, URITo.N. - Unit for Research and Innovation on Forensic Toxicology, Neuroscience of Addiction and New Drugs. FT-DSS University of Florence Florence, Italy
| | - Claudia Rimondo
- Department of Diagnostic and Public Health, University of Verona Verona, Italy
| | - Maddalena Mereu
- Departmentof Pharmaceutical and Pharmacological Sciences, University of Padua Padua, Italy
| | - Matteo Marti
- Department of Life Sciences and Biotechnology, University of Ferrara Ferrara, Italy
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Araújo AM, Carvalho F, Bastos MDL, Guedes de Pinho P, Carvalho M. The hallucinogenic world of tryptamines: an updated review. Arch Toxicol 2015; 89:1151-73. [PMID: 25877327 DOI: 10.1007/s00204-015-1513-x] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 03/25/2015] [Indexed: 12/25/2022]
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Schifano F, Orsolini L, Duccio Papanti G, Corkery JM. Novel psychoactive substances of interest for psychiatry. World Psychiatry 2015; 14:15-26. [PMID: 25655145 PMCID: PMC4329884 DOI: 10.1002/wps.20174] [Citation(s) in RCA: 236] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Novel psychoactive substances include synthetic cannabinoids, cathinone derivatives, psychedelic phenethylamines, novel stimulants, synthetic opioids, tryptamine derivatives, phencyclidine-like dissociatives, piperazines, GABA-A/B receptor agonists, a range of prescribed medications, psychoactive plants/herbs, and a large series of performance and image enhancing drugs. Users are typically attracted by these substances due to their intense psychoactive effects and likely lack of detection in routine drug screenings. This paper aims at providing psychiatrists with updated knowledge of the clinical pharmacology and psychopathological consequences of the use of these substances. Indeed, these drugs act on a range of neurotransmitter pathways/receptors whose imbalance has been associated with psychopathological conditions, including dopamine, cannabinoid CB1, GABA-A/B, 5-HT2A, glutamate, and k opioid receptors. An overall approach in terms of clinical management is briefly discussed.
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Affiliation(s)
- Fabrizio Schifano
- School of Life and Medical Sciences, University of Hertfordshire, Hatfield, Herts, UK
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Tittarelli R, Mannocchi G, Pantano F, Romolo FS. Recreational use, analysis and toxicity of tryptamines. Curr Neuropharmacol 2015; 13:26-46. [PMID: 26074742 PMCID: PMC4462041 DOI: 10.2174/1570159x13666141210222409] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 10/25/2014] [Accepted: 10/25/2014] [Indexed: 11/22/2022] Open
Abstract
UNLABELLED The definition New psychoactive substances (NPS) refers to emerging drugs whose chemical structures are similar to other psychoactive compounds but not identical, representing a "legal" alternative to internationally controlled drugs. There are many categories of NPS, such as synthetic cannabinoids, synthetic cathinones, phenylethylamines, piperazines, ketamine derivatives and tryptamines. Tryptamines are naturally occurring compounds, which can derive from the amino acid tryptophan by several biosynthetic pathways: their structure is a combination of a benzene ring and a pyrrole ring, with the addition of a 2-carbon side chain. Tryptamines include serotonin and melatonin as well as other compounds known for their hallucinogenic properties, such as psilocybin in 'Magic mushrooms' and dimethyltryptamine (DMT) in Ayahuasca brews. AIM To review the scientific literature regarding tryptamines and their derivatives, providing a summary of all the available information about the structure of these compounds, their effects in relationship with the routes of administration, their pharmacology and toxicity, including articles reporting cases of death related to intake of these substances. METHODS A comprehensive review of the published scientific literature was performed, using also non peer-reviewed information sources, such as books, government publications and drug user web fora. CONCLUSIONS Information from Internet and from published scientific literature, organized in the way we proposed in this review, provides an effective tool for specialists facing the emerging NPS threat to public health and public security, including the personnel working in Emergency Department.
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Affiliation(s)
- Roberta Tittarelli
- Legal Medicine Section, Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, “Sapienza” University of Rome, Viale Regina Elena, 336, 00161 Rome, Italy
| | - Giulio Mannocchi
- Legal Medicine Section, Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, “Sapienza” University of Rome, Viale Regina Elena, 336, 00161 Rome, Italy
| | - Flaminia Pantano
- Legal Medicine Section, Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, “Sapienza” University of Rome, Viale Regina Elena, 336, 00161 Rome, Italy
| | - Francesco Saverio Romolo
- Legal Medicine Section, Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, “Sapienza” University of Rome, Viale Regina Elena, 336, 00161 Rome, Italy
- Institut de Police Scientifique, Université de Lausanne, Batochime, 1015 Lausanne, Switzerland
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Blough BE, Landavazo A, Partilla JS, Decker AM, Page KM, Baumann MH, Rothman RB. Alpha-ethyltryptamines as dual dopamine-serotonin releasers. Bioorg Med Chem Lett 2014; 24:4754-4758. [PMID: 25193229 DOI: 10.1016/j.bmcl.2014.07.062] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/19/2014] [Accepted: 07/22/2014] [Indexed: 11/26/2022]
Abstract
The dopamine (DA), serotonin (5-HT), and norepinephrine (NE) transporter releasing activity and serotonin-2A (5-HT2A) receptor agonist activity of a series of substituted tryptamines are reported. Three compounds, 7b, (+)-7d and 7f, were found to be potent dual DA/5-HT releasers and were >10-fold less potent as NE releasers. Additionally, these compounds had different activity profiles at the 5-HT2A receptor. The unique combination of dual DA/5-HT releasing activity and 5-HT2A receptor activity suggests that these compounds could represent a new class of neurotransmitter releasers with therapeutic potential.
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Affiliation(s)
- Bruce E Blough
- Center for Drug Discovery, Research Triangle Institute, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA.
| | - Antonio Landavazo
- Center for Drug Discovery, Research Triangle Institute, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA
| | - John S Partilla
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Ann M Decker
- Center for Drug Discovery, Research Triangle Institute, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA
| | - Kevin M Page
- Center for Drug Discovery, Research Triangle Institute, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA
| | - Michael H Baumann
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Richard B Rothman
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
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Kamour A, James D, Spears R, Cooper G, Lupton DJ, Eddleston M, Thompson JP, Vale AJ, Thanacoody HKR, Hill SL, Thomas SHL. Patterns of presentation and clinical toxicity after reported use of alpha methyltryptamine in the United Kingdom. A report from the UK National Poisons Information Service. Clin Toxicol (Phila) 2014; 52:192-7. [DOI: 10.3109/15563650.2014.885983] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Herraiz T, Brandt SD. 5-(2-Aminopropyl)indole (5-IT): a psychoactive substance used for recreational purposes is an inhibitor of human monoamine oxidase (MAO). Drug Test Anal 2013; 6:607-13. [DOI: 10.1002/dta.1530] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 08/03/2013] [Accepted: 08/04/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Tomás Herraiz
- Spanish National Research Council (CSIC); Instituto de Ciencia y Tecnología de Alimentos y Nutrición (ICTAN); Juan de la Cierva 3 28006 Madrid Spain
| | - Simon D. Brandt
- School of Pharmacy & Biomolecular Sciences; Liverpool John Moores University; Byrom Street Liverpool L3 3AF UK
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Lessin AW, Long RF, Parkes MW. The central stimulant properties of some substituted indolylalkylamines and beta-carbolines and their activities as inhibitors of monoamine oxidase and the uptake of 5-hydroxytryptamine. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 2010; 29:70-9. [PMID: 19108241 DOI: 10.1111/j.1476-5381.1967.tb01940.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Glennon RA, Bondareva T, Young R. alpha-Ethyltryptamine (alpha-ET) as a discriminative stimulus in rats. Pharmacol Biochem Behav 2006; 85:448-53. [PMID: 17112572 PMCID: PMC2565776 DOI: 10.1016/j.pbb.2006.09.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 09/11/2006] [Accepted: 09/27/2006] [Indexed: 11/23/2022]
Abstract
alpha-Ethyltryptamine (etryptamine, alpha-ET) is a drug of abuse that first appeared on the clandestine market in the mid-1980s. Its pharmacological actions are poorly understood. In this investigation, it is reported for the first time that alpha-ET serves as a training drug in drug discrimination studies. Male Sprague-Dawley rats were trained to discriminate (30-min pretreatment time) 2.5 mg/kg of alpha-ET (ED(50)=1.3 mg/kg) from saline vehicle using a standard two-lever operant paradigm and a VI-15s schedule of reinforcement for appetitive reward. Once established, the alpha-ET stimulus was shown to have an onset to action of 30 min and a duration of effect of at least 4 h. In tests of stimulus generalization (substitution), the alpha-ET stimulus generalized to S(-)alpha-ET (ED(50)=1.6 mg/kg) and R(+)alpha-ET (ED(50)=1.3 mg/kg). Tests of stimulus generalization were also conducted with prototypical phenylisopropylamines: (+)amphetamine, 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM), and N-methyl-1-(4-methoxyphenyl)-2-aminopropane (PMMA). The alpha-ET stimulus generalized to DOM (ED(50)=0.4 mg/kg) and PMMA (ED(50)=0.7 mg/kg), but only partially generalized (ca. 40% maximal drug-appropriate responding) to (+)amphetamine. The results suggest that alpha-ET produces a complex stimulus.
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Affiliation(s)
- Richard A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298-0540, USA.
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LESSIN AW, LONG RF, PARKES MW. THE EFFECTS OF ALPHA-ALKYL SUBSTITUTED TRYPTAMINES ON 5-HYDROXYTRYPTAMINE UPTAKE BY BLOOD PLATELETS. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 1996; 24:68-75. [PMID: 14302000 PMCID: PMC1704040 DOI: 10.1111/j.1476-5381.1965.tb02080.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bülbring E, Gershon MD. 5-hydroxytryptamine participation in the vagal inhibitory innervation of the stomach. J Physiol 1967; 192:823-46. [PMID: 4383454 PMCID: PMC1365545 DOI: 10.1113/jphysiol.1967.sp008334] [Citation(s) in RCA: 170] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
1. Intraluminal pressure was recorded from the isolated guinea-pig and mouse stomach with the vagus and sympathetic nerves attached.2. The response to vagal stimulation, which consists of an excitatory and an inhibitory component, resembled the response to 5-hydroxytryptamine (5-HT), which has no direct action on the muscle but acts on intrinsic excitatory and inhibitory ganglia.3. In the presence of hyoscine, the effect of vagal stimulation, of nicotinic compounds and of 5-HT were all purely relaxant. Competitive block of ganglionic receptors for acetylcholine reduced the vagal relaxation without antagonizing 5-HT. Specific desensitization of ganglionic receptors for 5-HT reduced the vagal relaxation without antagonizing nicotinic compounds.4. During the early phase of the blocking action of nicotine, responses to vagal stimulation and to 5-HT were both abolished. As the non-specific antagonism changed to the later phase of specific antagonism to acetylcholine, the inhibitory (but not the excitatory) component of the vagal response recovered partially, in parallel with the recovery of the relaxant effect of 5-HT.5. The vagal inhibitory effect was completely abolished only when competitive block of acetylcholine receptors was combined with desensitization of 5-HT receptors.6. Stimulation of the mouse stomach (after asphyxiation of the mucosa and exclusion of the luminal content) in the presence of hyoscine caused the release of 5-HT; this release was blocked by tetrodotoxin.7. The results, together with previous observations that 5-HT is contained within preganglionic nerve fibres in the myenteric plexus, are consistent with the hypothesis that 5-HT, with acetylcholine, may be a neurotransmitter in the vagal inhibitory innervation of the stomach.
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